Method and apparatus for dewatering coal tailings and slurries and removing contaminants therefrom

ABSTRACT

A method of dewatering a mixture of coal tailings, water and contaminants comprising the steps of (a) providing a tank having a base surface and introducing said mixture of coal, tailings, water, and contaminants to said tank and allowing said coal tailings to settle on said base surface, (b) removing the coal tailings from said base surface of said tank along with water and contaminants and then separating said water and at least some of said contaminants from said coal tailings wherein said separated contaminants are suspended in said separated water, (c) adding an agent selected from one or more of the group consisting of a coagulant and a flocculent to said water and suspended contaminants separated from the coal tailings in step (b), (d) allowing the agent added in step (c) to coagulate or flocculate with the suspended contaminants to form a coagulated or flocculated mass and a quantity of supernatant water, and (e) separating the coagulated or flocculated mass formed in step (d) from the quantity of supernatant water formed in step (d). An apparatus for practicing the method is also enclosed. A similar method and apparatus for dewatering and recovering process water from substantially clean coal slurry products and mineral slurries is also disclosed.

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] The present invention relates to methods and apparatus forseparating solids from liquids and other solids and, in particular, todewatering and decontaminating coal tailings, clean coal products, andmineral slurries. The present invention also relates to methods andapparatus for liquid purification and, in particular, to methods andapparatus for recovering decontaminated process water from coaltailings, clean coal products and mineral slurries.

[0003] 2. Background Information

[0004] In the cleaning or washing of coal for commercial use as a fueland the like, the uncombustible ash content of coal is usually removedto enhance the heat content of the coal. Reduction in the ash contentresults in savings in transportation and ash disposal costs. Othermaterials frequently occurring with coals that may be removed in washingoperations include various clays and sulfides. Such clays commonlyinclude aericite (KAl₂(AlSi₃O)(OH)₁₂, smectite (Al₂Si₄O₁₀(OH₁₂)H₂O, andkaolinite clays (Al₂Si₄O₅(OH)₄. Sulfides are usually pyrite (FeS₄(isometrical)).

[0005] During the processing of coal to effect such washing, a coalrefuse slurry is generated. This slurry comprises coal fines known astailings, and contaminants such as clay and mud suspended in plantprocess water. Due to the high volume of water used in the processing ofcoal, it is necessary to reclaim the wash water for recirculation in theplant. The concentrated solids are sent to an impoundment pound fordisposal. In some cases in which coal washing plants have been operatingfor years, such slurry pounds may occupy hundreds of acres and maycontain millions of tons of coal fines. These slurry ponds may alsocontain coal slurry to a depth of 70-150 feet. Such slurry ponds notonly occupy a great deal of valuable land, but they also contain aconsiderable amount of energy and water resources.

[0006] Clean coal slurries are also used as, for example, an effectiveand cost effective means for transporting coal over distances from theplace of production to the place of use.

[0007] The prior art discloses various methods and apparatuses fordewatering and decontaminating refuse pond coal slurries and fordewatering clean coal slurries.

[0008] U.S. Pat. No. 4,128,474 to Ennis discloses a wet mechanicalprocess for cleaning, upgrading and dewatering fine coal. The processprovides for forming an aqueous feed slurry of fine coal and itsassociated contaminant particles wherein all particles have a particleportion size of less than about 6 mm. ranging to zero. The feed slurryis separated into coal slurry and refuse slurry portions in a spiralgravity concentrator by removing contaminants having a particle sizegreater than about 0.15 mm. The concentrated coal slurry is then fed toa hydrocyclone separator where all the ultra-fine silt material having aparticle size of less than 0.15 mm. is removed and the coal particlefraction 6 mm. to 0.15 mm. is accumulated and thoroughly dewatered.

[0009] U.S. Pat. No. 4,257,879 to Bogenschneider, et al. discloses amethod for optimizing coal slurry dewatering process in the fine graincontent is regulated to keep the filter cake at a constant level. Aseparation of the slurry into a predominantly relatively fine grainfraction and a relatively coarse grain fraction, with the division pointbeing between about 0.03 and 0.15 mm. is carried out with a formation ifa coal agglomerate from the fine grain fraction is accomplished.

[0010] U.S. Pat. No. 4,526,121 to Shudo, et al. discloses a ship fortreating a coal slurry comprising a pair of opposed trays disposed inthe vicinity of the upper deck for causing the coal slurry suppliedthereto to flow forward and delivering the slurry, a slanting dewateringscreen disposed below each of the trays for dewatering the coal slurrydelivered from the tray to separate a particulate coal fraction havingrelatively large particle sizes and conveyors for transporting to aspecified position on the upper deck the particulate coal fractiondewatered and falling off the screen.

[0011] U.S. Pat. No. 4,620,672 to Liebson, et al. discloses a system forconverting a coal slurry flowable through a pipeline to a coal watermixture capable of being rendered suitable for direct combustion in aboiler. The system includes a pipeline extending from a region adjacentto a mine or source of a coal to a region adjacent to a boiler orfurnace at which combustion is to take place. In the furnace region, theslurry from the pipeline is directed into a holding space, such as apond, from which it is directed to a grinding apparatus. On the way tothe grinding apparatus from the pond, a side stream of the slurry isdirected through a dewatering apparatus where the concentration of theside stream is increased form 50-55 weight percent of solids to about70-80 weight percent of solids. The outlet of dewatering apparatus isdirected back to the main flow of slurry from the pond, and the mainflow enters the grinding apparatus where the slurry is ground to aparticle size suitable for combustion, such as 70-80% weight percent ofsolids at 200 mesh. The ground slurry can then be directed into a smallagitated tank and from this tank it can be directed into the boiler orfurnace for combustion.

[0012] U.S. Pat. No. 4,810,371 to Fonseca discloses a process forautomating fine coal cleaning including monitoring the operation of aflotation cell for separating coal from ash impurities by automaticallydetecting the coal content of the tailings from the cell and controllingthe supply of additives to the cell to optimize slurry coal recovery andautomatically monitoring the fluid level of the coal slurry in adewatering filter tub to control the supply of additives to the filtertub and functioning of a dewatering filter.

[0013] U.S. Pat. No. 5,236,596 to Greenwald, Sr. discloses a method andapparatus for dewatering an aqueous coal slurry which includes impartinghigh shear forces to the aqueous coal slurry in the presence of apeptizing agent to render coal particles hydrophobic by stripping clayfrom the coal particles and peptizing the clay in the aqueous medium ofthe slurry. The slurry is separating to recover coal particles and theaqueous medium is draining medium from the hydrophobic of the coalparticles.

[0014] U.S. Pat. No. 5,256,169 to Roe discloses a process for dewateringand agglomerating fine coal. The process consists of treating an aqueousfine coal slurry with a chemical binding agent prior to filtration ordrying. The preferred chemical binding agent is an emulsifiable processoil. Efficiencies in dewatering and in lowered low dustiness of thetreated coal are disclosed.

[0015] U.S. Pat. No. 5,346,630 to Kenney discloses a process for thevacuum filtering of coal slurries. Dewatering of a filter cake isachieved by contacting the coal with a C(8) to C(2Q) aliphaticcarboxylic acid or a derivative thereof, especially sodium oleate.

[0016] U.S. Pat. No. 5,476,522 to Kerr, et al. discloses a method forconcentrating coal tailings and for dewatering coal products employing acopolymer of diallyidimethlylammonium halide and a vinyl alkoxysilane,preferably a copolymer of diallyldimethlylammonium chloride andvinyltrimethoxysilane as a coagulant. The method for concentrating coaltailings comprises steps of feeding the coal tailings to a thickener;treating the coal tailings with the coagulant, discharging substantiallyconcentrated tailing; and withdrawing substantially clarified liquidfrom the thickener. A method for dewatering coal products containingwater comprising the steps of feeding the clean coal containing water toa twin belt filter press; treating said coal with an effective amount ofa copolymer coagulant of diallyldimethlylammonium halide and vinylalkoxysilane, preferably diallyldimethlylammonium chloride and vinyltrimethoxysilane is also disclosed. The method encompasses removingwater from the coal product through the addition of the subject polymercoagulant; removing the dewatered clean coal product from the filter;and withdrawing the recycled water through the filter.

[0017] U.S. Pat. No. 5,622,647 to Kerr, et al. discloses a method fordewatering coal tailings, clean coal products and mineral slurries, aswell as for the clarification of water contained in coal refuseslurries, employing a copolymer of diallyldimethlylammonium halide and avinyl alkoxysilane, which is preferably a copolymer ofdiallyidimethlylammonium chloride and vinyltrimethoxysilane as acoagulant is disclosed.

[0018] U.S. Pat. No. 5,795,484 to Greenwald, Sr. discloses a method andapparatus for dewatering an ultra-fine coal particle fraction forms acoal product with particles that are dilatant due to the mechanicalstripping of the clay contaminants from the coal surface and thesubdividing of the clay to clay platelets which are peptized to maintaindiscreetness in an aqueous slurry. The coal particles are unflocculatedand can produce an aqueously permeable barrier on a sieve. The ultrafinecoal product has an increase of 100-150 BTU per pound and when combustedreduced Nox production of 2040% is realized. In a 15*0 micron coalfraction, the sulphur content is significantly reduced.

[0019] U.S. Pat. No. 6,042,732 to Jankowski, et al. discloses a methodfor dewatering coal tailings, clean coal products and mineral slurrieswith an effective coagulating amount of a combination of a cationicpolymer and a starch. A preferred cationic polymer ispoly(dimethylaminoethylaerylate methyl chloride quaternary salt) andpreferred starches are unmodified.

[0020] A need still exists for a further improved method and apparatusfor dewatering and decontaminating coal tailings and recovering watertherefrom.

[0021] A need also still exists for a further improved method andapparatus for dewatering and decontaminating clean coal slurry productsand mineral slurries and reconveying process water therefrom.

SUMMARY OF THE INVENTION

[0022] It is an object of the present invention to provide an efficientand cost effective method and apparatus for dewatering coal tailings andfor removing contaminants therefrom.

[0023] It is a further object of the present invention to provide anefficient and cost effective method and apparatus for dewateringsubstantially clean coal slurries and to remove any contaminants presenttherefrom.

[0024] It is a further object of the present invention to provide anefficient and cost effective method and apparatus for dewatering othermineral slurries and to remove any contaminants therefrom.

[0025] It is a further object of the present invention to provide anefficient and cost effective method and apparatus for reclaimingvaluable water from coal refuse slurry ponds.

[0026] It is a further object of the present invention to provide anefficient and cost effective method and apparatus for reclaimingvaluable process water from substantially clear coal slurry products.

[0027] It is a further object of the present invention to provide anefficient and cost effective method and apparatus for reclaimingvaluable process water from other mineral slurries.

[0028] It is a further object of the present invention to provide anefficient and cost effective method and apparatus for reclaimingvaluable land resources from land previously occupied by coal refuseslurry ponds.

[0029] It is a further object of the present invention to provide anefficient and cost effective method and apparatus for a ameliorating oreliminating any environmental risk to soils and water tables which maybe presented by coal refuse slurry ponds.

[0030] It is a further object of the present invention to provide amethod and apparatus for efficiently and cost effectively dewateringcoal tailings and removing contaminants therefrom which is mobile andcan readily be moved to coal refuse slurry ponds in remote, hilly ormountainous locations.

[0031] It is a still further object of the present invention to providea method and apparatus for efficiently and cost effectively dewateringcoal tailings and removing contaminants therefrom which is compact andadapted to being used on sites where the available land for suchoperations is limited or where such available land is located on hilly,mountainous or otherwise uneven terrains.

[0032] These and other objects of the present invention are provided bythe method of the present invention, which is a method of dewatering amixture of coal tailings, water and contaminants comprising the steps of(a) providing a tank having a base surface and introducing said mixtureof coal, tailings, water, and contaminants to said tank and allowingsaid coal tailings to settle on said base surface, (b) removing the coaltailings from said base surface of said tank along with water andcontaminants and then separating said water and at least some of saidcontaminants from said coal tailings wherein said separated contaminantsare suspended in said separated water, (c) adding an agent selected fromone or more of the group consisting of a coagulant and a flocculant tosaid water and suspended contaminants separated from the coal tailingsin step (b), (d) allowing the agent added in step (c) to coagulate orflocculate with the suspended contaminants to form a coagulated orflocculated mass and a quantity of supernatant water, and (e) separatingthe coagulated or flocculated mass formed in step (d) from the quantityof supernatant water formed in step (d).

[0033] This coal slurry cleanup is unique in that it does not matter asto the size or volume of a pond. The system consists of a completelyportable plant and can be moved from one location to another in a matterof days. It operates on air, hydraulics and electric generator, and canbe put in very remote areas. A dredge is put into a slurry pond to pumpthe material. This material consists of coal, water, clay, mud, orwhatever else may have been deposited. The dredge must be adequate insize to pump the volume of material and water needed to operate theplant. In most cases, a volume of 800 GPM to 1500 GPM will be required.This coal slurry cleanup consists of a method where a portable plant isassembled wherever coal slurry is found to be recoverable, normallywhere coal prep plants have been operating for a period of time. Theslurry will then be brought to the plant and processed to where therewill be a steady stream of coal from a discharge belt to a stockpile. Abackflow of waste water will flow to a clarifier tank which will allowthe clay, mud and other heavy materials to settle out. The heavymaterial will then be pumped to a hyraulic press where the water isseparated from solids. The solids will then be discharged to a stockpileand the water will return to the pond for use or can be let into a waterstream.

[0034] Also encompassed within the present invention is a method ofdewatering substantially clean coal slurry products comprising the stepsof (a) providing a tank having a base surface and introducing thesubstantially clean coal product into said tank and allowing said finecoal to settle on said base surface, (b) removing the fine coal fromsaid base surface of said tank along with water and contaminants andthen separating said water and at least some of said contaminants fromsaid fine coal wherein said separated contaminants are suspended in saidseparated water, (c) adding an agent selected from one or more of thegroup consisting of a coagulant and a flocculant to said water andsuspended contaminants separated from the coal tailings in step (b), (d)allowing the agent added in step (c) to coagulate or flocculate with thesuspended contaminants to form a coagulated or flocculated mass and aquantity of supernatant water, and (e) separating the coagulated orflocculated mass formed in step (d) from the quantity of supernatantwater formed in step (d).

[0035] Also encompassed within the present invention is a method ofdewatering other mineral slurries comprising the steps of (a) providinga tank having a base surface and introducing said mineral slurry intosaid tank and allowing said mineral fines to settle on said basesurface, (b) removing the mineral fines from said base surface of saidtank along with water and contaminants and then separating said waterand at least some of said contaminants from said coal tailings whereinsaid separated contaminants are suspended in said separated water, (c)adding an agent selected from one or more of the group consisting of acoagulant and a flocculant to said water and suspended contaminantsseparated from the coal tailings in step (b), (d) allowing the agentadded in step (c) to coagulate or flocculate with the suspendedcontaminants to form a coagulated or flocculated mass and a quantity ofsupernatant water, and (e) separating the coagulated or flocculated massformed in step (d) from the quantity of supernatant water formed in step(d).

[0036] Also encompassed within the present invention is an apparatus foruse in processing a liquid and at least one solid particulate materialmixed with in said liquid said apparatus comprising a tank having afront end and a rear end, a base surface and a peripheral wall, an inputpoint positioned adjacent the rear end of the tank extending generallyupwardly from and surrounding the base wall, an output point positionedadjacent the front end of the, a particle collection area positioned onthe base surface beneath the input point, and means for conveying theparticles extending from adjacent the particle collection area to theoutput point.

[0037] Also encompassed within the present invention is an apparatus foruse in processing a liquid and at least one solid particulate materialmixed with liquid. This apparatus includes a tank having a front rearend, a base surface and a lateral wall having an upper rim. An inputpoint is positioned adjacent the rear end of the tank adjacent the upperrim of the tank. An output point is positioned adjacent the front end ofthe tank. A particle collection area is positioned on the base surfacebeneath the input point, and a particle conveyor means extends fromadjacent the particle collection area to the output point. There is ameans for separating particles and water removed from the tank, a meansfor adding a coagulant or flocculant to the water, a second tankdirectly connected to the first tank, and means for removing acoagulated or flocculated mass from clarified water.

[0038] Also encompassed within the present invention is an apparatus forreducing the concentration of a particulate material and a liquid. Theapparatus has a flow cavity having an input opening for the liquid withsuspended particulate material and a restricted output opening forparticulate material. The flow cavity has at least one perforated wallhaving an outer surface from which liquid having a reduced concentrationof particulate material is collected.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The preferred embodiment of the invention, illustrative of thebest mode in which applicant contemplated applying the principles, isset forth in the following description and is shown in the drawings andis particularly and distinctly pointed out and set forth in the appendedclaims.

[0040]FIG. 1 is a perspective view of the apparatus used in a preferredembodiment of the method of the present invention;

[0041]FIG. 2 is a detailed vertical cross sectional view of a preferredembodiment of the drag tank similar to the one shown in FIG. 1;

[0042]FIG. 3 is a top plan view of the drag tank apparatus shown in FIG.2;

[0043]FIG. 4 is a cross sectional view through 4-4 in FIG. 3;

[0044]FIG. 5 is a cutaway front elevational view similar to the settlingtank shown in FIG. 1;

[0045]FIG. 6 is a top plan view of the hydraulic press similar to thehydraulic press shown in FIG. 1;

[0046]FIG. 7 is a side elevational view of the hydraulic press shown inFIG. 6;

[0047]FIG. 8. Is a front elevational view of the hydraulic filter pressshown in FIG. 6;

[0048]FIG. 9 is a detailed view of circle 9 in FIG. 8; and

[0049]FIG. 10 is a detailed view of circle 10 in FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] Referring to FIG. 1 there is a pond 10 with coal fine washingtailings or “coal tailings” having dimensions from about 0.25 inch downto about 0.001 inch.

[0051] Along with these coal tailings, there are contaminants which mayinclude clay, silt, mud and pyrite. These coal tailings are removed frompond 10 by a dredge 12 along with water in line 14 to a tank 16 which isreferred to herein at various points as a “drag tank”. Preferably, theamount of water in the mixture of fine coal, contaminants and water inline 14 is adjusted to from about 60 percent to about 40 percent byweight. The drag tank 16 has an input point 18 and is mounted on a truckmount 20 so as to be mobile. The tank 16 contains a water, fine coal andcontaminant mixture 22 and has an output point 24 for removal of finecoal and contaminants mixed with water. The tank 16 also has a dischargetrough 26 for removal of water 22 adjacent a rim 28. There is a conveyorsystem 30 which extends from the output point 24 of the tank 16 toremove fine coal and water 32 to a centrifuge 34. Preferably, the amountof water in the mixture of fine coal, contaminants and water 34 is fromabout 10 percent to about 40 percent by weight. This centrifuge 34separates clean fine coal 36 and deposits this fine coal on a conveyorbelt 38 for removal to a stored fine coal deposit 40. Preferably thecentrifuge is a model no. EBW-36 centrifuge manufactured by CMI, Inc. ofSt. Louis, Mo. which is preferably operated at from about 1800 RPM toabout 4200 RPM. Those skilled in the art will appreciate that otherequivalent means of separating particles from water such as a filterpress, a screw press, a belt filter, or a screen may be substituted forthe centrifuge 34. It is believed, however, that the centrifuge 34 wouldbe the preferred means of separating such fine coal from water sinceclay contaminants may tend to adhere to coal particles, and centrifugingthe fine coal and water may create sufficient shear to remove the clayfrom the coal particles. Such clay, which may be in a platelet shape,may become suspended in the water once removed from coal particles.Extending from the centrifuge 34 there is a centrifuge output line 42which removes water and contaminants to a settling tank 44. A settlingtank discharge line 46 removes water and suspended contaminants to apolymer addition tank 48 from where polymer addition tank output line 50extends to the discharge trough 26 from the tank 16 by means of which acoagulating or flocculating agent is added to the water in dischargetrough 26. This coagulating or flocculating agent may be an anionic orcationic polymer or a nonionic emulsion polymer. Such flocculents arepreferably introduced into the total amount of water being introduced tothe clarifier tank in an amount of from about 2 percent to about 6percent by weight. The polymer may also be used with a starch in themanner disclosed, for example, in the aforesaid U.S. Pat. No. 6,042,732to Jankowski, et al. which also discloses suitable flocculent polymersfor use in the method of this invention. Specific suitable flocculentpolymers for use in the method of the present invention are alsodisclosed in the aforesaid U.S. Pat. Nos. 5,476,522 and 5,622,647 bothto Kerr, et al. Inorganic coagulants which are known in the art such asalem and iron salts may also be used. The discharge trough 26 emptiesinto a clarifier tank 52 at a tank input 54. The clarifier tank 52 isset on a track mount 58 to allow the clarifier tank 52 to be mobile. Theclarifier tank 52 has three settling sections 60, 62 and 64 which emptyrespectively into discharge lines 66, 68 and 70 which connect tohydraulic filter press 72. The hydraulic filter press 72 has a wateroutput line 74. The hydraulic filter press 72 also has a plurality ofsolid output apertures as at aperture 76 where clay and othercontaminants 78 are outputted as solids onto conveyor belt 80. Thestructure and operation of this hydraulic filter press 72 is essentiallythe same as the embodiment shown in FIGS. 6-10 and described in greaterdetail hereafter. While the centrifuge 34, settling tank 44, polymeraddition tank 48, and hydraulic filter press 72 are not shown with atrailer mount, it will be understood that these components of the entireassembly, along with their associated piping and belting systems, may bereadily disassembled and loaded onto a trailer for transporting suchcomponents to remote operation sites. Such sites may be located inhilly, mountainous, or uneven terrain and the entire apparatus may bereadily and quickly reassembled for operation in an area where onlyrelatively small amounts of level land are available. In practice, it isfound that the entire assembly may be transported to an operations siteon from about 3 to 5 tractor trailer combinations. It is also found thatthe entire apparatus may be assembled for use on only about 5,600 to15,600 square feet of relatively level land.

[0052] Referring to FIGS. 2-4, another embodiment of the drag tankdescribed is shown generally at numeral 82. This tank has a pair ofsidewalls 84 and 86, a rear end wall 88, front oblique walls 90 and 92,a front end wall 94, and a base wall 96. The tank 82 also has a waterand coal fine mixture input point 98 by means of which the mixture isadded to water 100 in the tank 82 which is maintained beneath the rim102 of the tank 82 by a water discharge ramp 104. Directly beneath thewater and coal fine input 98 there are collected fine coal 106 on acollection area 108 on the base wall 96. There is a continuous conveyorchain 110 with a plurality of outwardly extending paddles as at paddle112 for moving the collected fine coal 106 to a solids discharge point114. As an alternative to using the conveyor chain 110, a conveyor beltmay be used. As an alternative to using the paddles as at paddle 112,scoop or shovel shaped devices may be used to move the collected finecoal 106 to the solids discharge point 114. The continuous conveyor belt110 moves on rollers 116, 118, 120, 122, 124, 126, 128, and 130. Inparallel spaced relation to the conveyor belt is a central ramp 132which is angled upwardly and has a terminal downwardly angled section134. Preferably the angle of this central ramp 132 will be from about20° to about 40° above the horizontal. Referring particularly to FIG. 4,it will be seen that the sidewalls 84 and 86 have inwardly slopedsections 136 and 138 respectively. Preferably the side walls 84 and 86from angled inwardly from the vertical by from about 40° to about 60°.

[0053] Referring to FIG. 5, another embodiment of the clarification tankis shown generally at numeral 140 which includes a tank input line 142and a tank output line 144. In this embodiment, there are four settlingsections 146, 148, 150, and 152. These settling sections have high flocdensity areas 154, 156, 158, and 160. Above these high floc densityareas there is a clarified supernatant water area 162. The settlingsections are respectively discharged in lines 164, 166, 168, and 170.The concentration of floc will be greatest in settling section 146, andwill decrease from section 148 to section 152, wherein the flocconcentration will be the lowest in section 152. It will be appreciatedthat more of fewer settling sections may be used to optimize results inparticular situations.

[0054] Referring to FIGS. 6-10, another embodiment of the hydraulicfilter press element is shown generally at numeral 172 which has aninput side 174 and a discharge side 176. On the input side 174 there areinput line connections 178, 180, 182, and 184. Adjacent the input side174 there is a transverse trough 186 from which a water discharge line188 extends for discharge of purified water from the system. Thehydraulic filter press 172 also has lateral walls 190 and 192, andlongitudinal troughs 194, 196, 198, 200, 202, 204, 206, and 208 areinterposed. Extending between the lateral walls 190 and 192 there is atransverse wall 210. On the discharge side 176 of the hydraulic filterpress 172, there are restricted output apertures 212, 214, 216, 218,220, 222, 224, and 226. The hydraulic filter press 172 also has a basewall 228 and a top wall 230. The hydraulic filter press 172 is supportedby piston and cylinder combination 232 which rests on a base 234 and isconnected to a axle 236. At its opposed side the hydraulic filter press172 is supported by piston and cylinder combination 238 which is mountedon a base 240 and attached to an axle 242. These piston and cylindercombinations 232 and 238 cooperatively adjust the height of thehydraulic filter press 172 from a lowered position as shown in solidlines and to an elevated inclined position as is shown at 172′ inphantom lines in FIG. 7. The angle of inclination of the position of theelevated hydraulic position of hydraulic filter press 172 will be in therange of 0° to about 40° and depending on the concentration of theparticles in the water often more preferably in the range of about 20°to about 40°.

[0055] The hydraulic filter press 172 includes a flow cavity 244 whichis bonded by the bottom wall 228, the top wall 230, side wall 246, sidewall 248, front wall 250 and rear wall 252. The top wall 230 has aperforated section 254 with a plurality of vertical perforationsconnecting to the flow cavity 244. Such perforations are shown as, forexample, perforations 256 and 258 in FIG. 10. Preferably, theseperforations are circular and about one inch in diameter and areseparated from each other by about ¼ inch so that there are about 108perforations per square foot on the perforated section 254 of top wall230. Positioned in parallel arrangements perpendicularly to wall 230there are a plurality of longitudinal walls 262, 264, 266, 268, 270,272, and 274 which define longitudinal troughs 194, 196, 198, 200, 202,204, 206, 208, and 210. Referring particularly to FIG. 10, it will beseen that the top wall 230 is comprised of a rigid top section 276, arigid bottom section, 278 and a medial textile section 280 which ispreferably comprised of a woven synthetic material. It will also be seenthat there are perforations as at perforation 282 in the top section 276and perforations as at perforation 284 in the bottom section. Eachperforation in the top section as at perforation 282 is verticallyaligned with another perforation as at perforation 284 in the bottomsection 278. The transverse end trough 186 is comprised of a front wall286, a rear wall 288, end wall 290, end wall 292, and base wall 294. Itwill be appreciated that the trough has an open top side. There is a gap296 between the bottom of the front wall 286 and the top wall 230 of theflow cavity 244. Because of this gap 296, water flows from longitudinaltroughs 194, 196, 198, 200, 202, 204, 206, 208, and 210 into thetransverse trough 186 and is then outputted through line 188. It willalso be seen that there are transverse pipes 298, 300, 302, and 304 forconveying water and suspended particles respectively from input lineconnections 178, 180, 182 and 184 to flow cavity 244. Positioned in theflow cavity 244 there is also a movable plunger 306 which includes ahead 308 and an extendable rod 310. There are apertures 312, 314, 316,and 318 through the head 308 to allow water with suspended particles topass from the rear to front side of the head 308. The plunger 306 wouldbe extendable to move particles to the front wall 250 of the flow cavity244. It will be understood that ordinarily the use of this plunger wouldbe optional and that in many situations water and suspended particleswill move to the front wall 250 merely by applying sufficient pressurefrom the rear wall 252. It will also be understood that the angle ofinclination of the filter press can be selected to most efficientlyremove the particles from the water. It will also be appreciated thatgreater angles of inclination will ordinarily be required when theconcentration of particulate matter in the water increases while at lowconcentrations it may be possible to use a 0° inclination. It will beappreciated that other equivalent means of separating the floc from thewater such as a centrifuge, a screw press, a belt filter, or a screencould, within the scope of this invention, be substituted for the filterpress 172.

EXAMPLE

[0056] A mixture of water and fine coal as well as clay, silt, mud, andpyrite contaminants are removed from a coal refuse slurry pond resultingfrom an industrial coal washing operation. This coal refuse slurry pondcontained coal tailings from the No. 4 and No. 5 Upper Kittanning andMiddle Kittanning seams mined in Tuscarawas County, Ohio. The mixturewas removed from the coal refuse slurry pond by means of a 8 inchperforated dredge at the rate of 1,200 gallons/minute. This mixture ofwater, fine coal and contaminants varied from about 60-80% by weightwater. The fine coal in this mixture varied from about 0.25 inch down toabout 0.001 inch. A typical sample of this input mixture of coaltailings, contaminants and water was recovered and analyzed as recoveredand after drying. The results of this analysis are shown in Table 1,wherein the ASTM method of analysis for each material is indicatedadjacent the material and all reported percentages are percent byweight. The coal tailings, contaminant and water mixture was moved in a8 inch diameter pipe at a speed of 1200 gallons/minute over a distanceof 500 feet to the input point of a drag tank generally as shown inFIGS. 2-4 above. In this drag tank the chain conveyors had flights thatwere 12 inches high and 24 inches wide inset at the bottom of the tank.The tank was approximately 8 feet wide and 18 feet long at water leveland had a capacity of 80 gallons. The conveyor continued above waterlevel so at least 10 feet of conveyor was used to dewater the coalbefore it was discharged. The tank was approximately 8 feet in depth atits rear end. The chain conveyor was operated at a speed of 10feet/minute. The water discharge trough at the rear end of the tank was6 feet wide and 10 inches deep at the rim of the rear end of the tank.Partially dewatered fine coal along with contaminants were removed bythe conveyor from the dreg tank at a rate of about 8 pounds/minute to anEB-48 centrifugal dryer which was procured from CMI, Inc. of St. Louis,Mo. Before being introduced to the centrifuge, this mixture of finecoal, contaminants and water had a water content of about 80 percent byweight. The centrifugal dryer was operated at a rate of 2,600 RPM toallow the fine coal to fluff out and be discharged to a conveyor belt ata rate of about 8 pounds/minute. Water effluent with suspendedcontaminants was removed from the centrifugal dryer at a discharge pipeat a rate of 10 gallons/minute to a 1,000 gallon capacity settling tank.Water along with settling contaminants were removed from this settlingtank at a rate of 4 gallons/minute to a polymer addition tank whereCALGON POL-E-Z 652 nonionic emulsion polymer which is commerciallyavailable from Nalco Chemical Company located at Naperville, Ill. sothat the overall amount of polymer used in the water and contaminantsintroduced to the clarifier was 3% by weight. Water along with suspendedcontaminants and the added polymer are then moved to the tank dischargetrough at a rate of 1,100 gallons/minute and added to the water beingremoved from the discharge tank and the water, contaminants and polymerswere then added to the clarifier tank at a rate of 1,100 gallons/minute.The clarifier tank had a length of 10 feet and a capacity of 500 gallonsand was similar to that shown in FIG. 5 above. Clarified supernatantwater was removed from the tank outlet type at a rate of 30gallons/minute. Floc and water were removed from each of the settlingsections of the tank at a rate of about 4 pounds/minute to a hydraulicfilter press by a 3 inch diaphragm pump operated by air. The hydraulicfilter press was similar to the one shown in FIGS. 6-10. The overalllength of this hydraulic filter press was 11 feet whereas thelongitudinal troughs were 10 feet in length and 1 foot in width. Theoverall width of the hydraulic filter press was 8 feet. The overallheight of the filter press was 18 inches while the height of thelongitudinal troughs of 12 inches. The metal insert for the hydraulicpress serves as a strainer and was made of ¼ inch punch plate which waskept 2 inches from all sides and the bottom so that the water can easilydischarge to the clear water. On the inside of the ¼ inch punch plate, apolyester and vinyl textile material was held to the sides with plasticstrips. The hydraulic filter press was positioned horizontally, i.e.with a 0° incline between its input and output ends. The hydraulicplunger was lined on the outside ends with a tube filled with grease sothat it could clean the cloth and not tear. The plunger operated onlywhen the press no longer took in material from the 3 inch diaphragmpumps. The plunger then pushed and caused the water left in the insertto discharge leaving dry solid clay and dirt to be removed to the stockpile area. Removal to the stock pile area was accomplished on dischargebelts which was 24 inches wide and approximately 20 feet long at a rateof 4 pounds/minute. The purified water discharged from both thehydraulic filter press and the clarifier tank was found to besubstantially free of both fine coal and suspended clay and othercontaminants. A typical sample of the moist solid output material wasrecovered and analyzed as recovered and after drying. The results ofthis analysis are shown in Table 2 wherein the ASTM method of analysisfor each material is indicated adjacent to the material and all reportedpercentages are percent by weight. for the purposes of this disclosure,“ash” is considered to be the solid incombustible material presentwithin the meaning of the cited ASTM method. TABLE Material As RecoveredAfter Drying ASTM Method Moisture 32.34% — D-2961 M, D-3173 Ash 29.07%42.96% D-3174 Sulfur  1.80%  2.66% D4239 Heat Content 4.987 BTU/lb 7,371BTU/lb D-1989

[0057] TABLE 2 Material As Received After Drying ASM Method Moisture13.00% — D-2961 M, D-3173 Ash  9.27% 10.66% D3174 Sulfur  2.00%  2.30%D-4239 Heat Content 10,918 BTU/lb 12,550 BTU/lb D-1989

[0058] Those skilled in the art will appreciate that the method andapparatus described herein may be used to dewater substantially cleancoal slurry products which are used in the art to transport fine coalfrom the point of production to the point of use. It will also beunderstood that the method and apparatus of the present invention willhave the advantage of removing a residual portion of any solidcontaminants which may be present in the coal slurry product so thatsuch contaminants are not present in either the fine coal or the processwater recovered from the coal slurry product.

[0059] In addition to the treatment of fine coal, dewatering is alsonecessary in other areas of mineral processing. Those skilled in the artwill appreciate that the method and apparatus of the present inventionmay be used to dewater and/or decontaminate a variety of such mineralslurries. Non-limiting examples of such slurries include sand andgravel, slurries of limestone, and ores, including, for example,taconite, trona, and titania. Guidance to those of ordinary skill in theart in coagulating or flocculating specific materials is contained, forexample, in Coagulation and Flocculation. Theory and Applications,edited by Bohuslav Dobias, University of Regensburg, Regensburg, Germany(published by Marcel Dekker, Inc., New York, 1993), particularly atpages 126-137, which is incorporated herein by reference.

[0060] The term “particle” as it is used herein, means any small pieceof a solid material, wherein that material may be one which is referredto as a particulate material as well as those materials which may beotherwise referred to in the art as a fine, powdered, pulverized,fragmented, or granular material or by like terms. For the purposes ofthis disclosure, a “particulate material” is a material comprised atleast in part of particles.

[0061] The term “suspended” as it is used herein refers to the conditionof a particle of a certain material or group of materials as being mixedwithin a liquid in a generally dispersed manner. The fact, however, thatsome particles of a material are heavier than other particles of thesame material and may tend, therefore, to collect nearer the bottom of aliquid body than such lighter particles, is not intended to mean thatthe overall group of particles of the material does not fall within thisdefinition.

[0062] The term “slurry”, as it is used herein, means any free flowingor flowable suspension of particles in a liquid. It is not intended thata mixture of particulate material and a liquid should be excluded fromthis definition merely because of the existence of a minor proportion ofoversized particles in this mixture.

[0063] It will be appreciated that the method and apparatus described inthis application is a simple and cost effective means for treating waterand fine coal and contaminants found in tailing ponds from commercialcoal washing operations. Water at ambient pressure which issubstantially free of both fine coal and clay and other contaminants isrecovered. Substantial amounts of dry, combustible fine coal are alsorecovered.

[0064] It will also be appreciated that the present invention providesan efficient and cost effective method and apparatus for dewateringsubstantially clean coal slurries and removing any contaminants presenttherefrom.

[0065] It will also be appreciated that the present invention providesan efficient and cost effective method and apparatus for dewateringother mineral slurries and removing any contaminants therefrom.

[0066] It will also be appreciated that the present invention providesan efficient and cost effective method and apparatus for reclaimingvaluable process water from substantially clean coal slurry products.

[0067] It will also be appreciated that the present invention providesan efficient and cost effective method and apparatus for reclaimingvaluable process water from other mineral slurries.

[0068] It will also be appreciated that the present invention providesan efficient and cost effective method and apparatus for reclaimingvaluable land resources from land previously occupied by coal refuseslurry ponds.

[0069] It will also be appreciated that the present invention providesan efficient and cost effective method and apparatus for a amelioratingor eliminating any environmental risk to soils and water tables whichmay be presented by coal refuse slurry ponds.

[0070] It will also be appreciated that the present invention provides amethod and apparatus for efficiently and cost effectively dewateringcoal tailings and removing contaminants therefrom which is mobile andcan readily be moved to coal refuse slurry ponds in remote, hilly ormountainous locations.

[0071] It will also be appreciated that the present invention provides amethod and apparatus for efficiently and cost effectively dewateringcoal tailings and removing contaminants therefrom which is compact andadapted to being used on sites where the available land for suchoperations is limited or where such available land is located on hilly,mountainous or otherwise uneven terrains.

[0072] Accordingly, the improved METHOD AND APPARATUS FOR DEWATERINGCOAL TAILINGS AND SLURRIES AND REMOVING CONTAMINANTS THEREFROM issimplified, provides an effective, safe, inexpensive, and efficientdevice which achieves all the enumerated objectives, provides foreliminating difficulties encountered with prior devices, and solvesproblems and obtains new results in the art.

[0073] In the foregoing description, certain terms have been used forbrevity, clearness, and understanding; but no unnecessary limitationsare to be implied therefrom beyond the requirement of the prior art,because such terms are used for descriptive purposes and are intended tobe broadly construed.

[0074] Moreover, the description and illustration of the invention is byway of example, and the scope of the invention is not limited to theexact details shown or described.

[0075] Having now described the features, discoveries, and principles ofthe invention, the manner in which the METHOD AND APPARATUS FORDEWATERING COAL TAILINGS AND SLURRIES AND REMOVING CONTAMINANTSTHEREFROM is practiced, constructed and used, the characteristics of theconstruction, and the advantageous new and useful results obtained; thenew and useful structures, devices, elements, arrangements, parts, andcombinations are set forth in the appended claims.

What is claimed:
 1. A method of dewatering a mixture of coal tailings,water and contaminants comprising the steps of: (a) providing a tankhaving a base surface and introducing said mixture of coal, tailings,water, and contaminants to said tank and allowing said coal tailings tosettle on said base surface; (b) removing the coal tailings from saidbase surface of said tank along with water and contaminants and thenseparating said water and at least some of said contaminants from saidcoal tailings wherein said separated contaminants are suspended in saidseparated water; (c) adding an agent selected from one or more of thegroup consisting of a coagulant and a flocculent to said water andsuspended contaminants separated from the coal tailings in step (b); (d)allowing the agent added in step (c) to coagulate or flocculate with thesuspended contaminants to form a coagulated or flocculated mass and aquantity of supernatant water; and (e) separating the coagulated orflocculated mass formed in step (d) from the quantity of supernatantwater formed in step (d).
 2. The method of claim 1 wherein the tank hasan entry point where the mixture of tailings, water and contaminants areintroduced to the tank in step (a) and a discharge point where the coaltailings, water and contaminants are removed in step (b) and said entrypoint and discharge point are both elevated from the base surface andsaid entry point is laterally displaced from said discharge point. 3.The method of claim 2 wherein the mixture of coal tailings, water andcontaminants is continuously introduced to the tank in step (a) and thecoal tailings, water and contaminants are continuously removed from thetank in step (b).
 4. The method of claim 3 wherein the coal tailings,water and contaminants are continuously removed from the tank by meansof a continuous conveyor system.
 5. The method of claim 1 wherein instep (b) the coal tailings are separated from the water and contaminantsby means of a centrifuge.
 6. The method of claim 5 wherein at least someof the contaminants removed with the coal tailings and water in step (b)are suspended in said removed water.
 7. The method of claim 5 wherein atleast some of the contaminants removed with the coal tailings and waterin step (b) are initially adhered to the coal tailings and are thenremoved from said coal tailings by centrifution to be suspended in thesaid removed water.
 8. The method of claim 1 wherein in step (c) one ormore of the group consisting of a coagulant and a flocculent is aflocculent and the flocculent is selected from the group consisting of acationic polymer, an anionic polymer, and a nonionic emulsion polymer.9. The method of claim 8 wherein in step (c) the flocculent is used inan amount of from about 2 percent to about 6 percent by weight of thewater and the suspended contaminants.
 10. The method of claim 1 whereinthe contaminants include clay.
 11. The method of claim 1 wherein thecontaminants are selected from one or more of the group consisting ofclay, silt, mud, and pyrite.
 12. The method of claim 6 wherein the coaltailings have a size of about ¼ inch and less.
 13. The method of claim 1wherein in step (c) the water and the suspended solid contaminants areintroduced to a clarifying second tank wherein coagulation orflocculation in said second tank in step (d) takes place.
 14. The methodof claim 1 wherein the coagulated or flocculated mass formed in claim(d) contains an additional quantity of water and at least some of saidadditional quantity of water is removed from the coagulated orflocculated mass after said coagulated or flocculated mass is separatedfrom the quantity of supernatant water in step (e).
 15. The method ofclaim 14 wherein at least some of said additional quantity of water isremoved from the coagulated or flocculated mass in a press.
 16. Themethod of claim 14 wherein the quantity of supernatant water and theadditional quantity of water separated from the coagulated orflocculated mas which are substantially free of contaminants.
 17. Themethod of claim 1 wherein in step (a), before being introduced to thefirst tank, the water in the mixture is adjusted so that the mixture isfrom about 60 percent to about 90 percent by weight water.
 18. Themethod of claim 1 wherein the coal tailings, contaminants and waterremoved from the tank in step (b) is from about 10 percent to about 40percent by weight water.
 19. The method of claim 13 wherein in step (c)the water and suspended contaminants separated from the coal tailing instep (b) is first removed to a settling third tank after which the agentselected from one or more of the group consisting of a coagulant and aflocculent is added before said water and suspended contaminants areadded to the clarifying second tank.
 20. The method of claim 13 whereinthe first tank has a rim and water flows directly from the first tankadjacent the rim to the clarifying third tank.
 21. A method ofdewatering a substantially clean coal slurry product comprising finecoal, contaminants and water comprising the steps of: (a) providing atank having a base surface and introducing said coal slurry product tosaid tank and allowing said coal tailings to settle on said basesurface; (b) removing the fine coal from said base surface of said tankalong with water and contaminants and then separating said water and atleast some of said contaminants from said fine coal wherein saidseparated contaminants are suspended in said separated water; (c) addingan agent selected from one or more of the group consisting of acoagulant and a flocculent to said water and suspended contaminantsseparated from the fine coal in step (b); (d) allowing the agent addedin step (c) to coagulate or flocculate with the suspended contaminantsto form a coagulated or flocculated mass and a quantity of supernatantwater; and (e) separating the coagulated or flocculated mass formed instep (d) from the quantity of supernatant water formed in step (d). 22.The method of claim 21 wherein the tank has an entry point where themixture of fine coal, water and contaminants are introduced to the tankin step (a) and a discharge point where the fine coal, water andcontaminants are removed in step (b) and said entry point and dischargepoint are both elevated from the base surface and said entry point islaterally displaced from said discharge point.
 23. The method of claim22 wherein the mixture of fine coal, water and contaminants iscontinuously introduced to the tank in step (a) and the coal tailings,water and contaminants are continuously removed from the tank in step(b).
 24. The method of claim 23 wherein the fine coal, water andcontaminants are continuously removed from the tank by means of acontinuous conveyor system.
 25. The method of claim 21 wherein in step(b) the fine coal is separated from the water and contaminants by meansof a centrifuge.
 26. The method of claim 25 wherein at least some of thecontaminants removed with the coal tailings and water in step (b) aresuspended in said removed water.
 27. The method of claim 25 wherein atleast some of the contaminants removed with the fine coal and water instep (b) are initially adhered to the coal tailings and are then removedfrom said coal tailings by centrifution to be suspended in the saidremoved water.
 28. The method of claim 21 wherein in step (c) one ormore of the group consisting of a coagulant and a flocculent is aflocculent and the flocculent is selected from the group consisting of acationic polymer, an anionic polymer, and a nonionic emulsion polymer.29. The method of claim 28 wherein in step (c) the flocculent is used inan amount of from about 2 percent to about 6 percent by weight of thewater and the suspended contaminants.
 30. The method of claim 21 whereinthe contaminants include clay.
 31. The method of claim 1 wherein thecontaminants are selected from one or more of the group consisting ofclay, silt, mud, and pyrite.
 32. The method of claim 21 wherein in step(c) the water and the suspended solid contaminants are introduced to aclarifying second tank wherein coagulation or flocculation in saidsecond tank in step (d) takes place.
 33. The method of claim 21 whereinthe coagulated or flocculated mass formed in claim (d) contains anadditional quantity of water and at least some of said additionalquantity of water is removed from the coagulated or flocculated massafter said coagulated or flocculated mass is separated from the quantityof supernatant water in step (e).
 34. The method of claim 33 wherein atleast some of said additional quantity of water is removed from thecoagulated or flocculated mass in a press.
 35. The method of claim 33wherein the quantity of supernatant water and the additional quantity ofwater separated from the coagulated or flocculated mas which aresubstantially free of contaminants.
 36. The method of claim 21 whereinin step (a), before being introduced to the first tank, the water in theslurry is adjusted so that the slurry is from about 60 percent to about90 percent by weight water.
 37. The method of claim 21 wherein the finecoal, contaminants and water removed from the tank in step (b) is fromabout 10 percent to about 40 percent by weight water.
 38. The method ofclaim 32 wherein in step (c) the water and suspended contaminantsseparated from the fine coal in step (b) is first removed to a settlingthird tank after which the agent selected from one or more of the groupconsisting of a coagulant and a flocculent is added before said waterand suspended contaminants are added to the clarifying second tank. 39.The method of claim 32 wherein the first tank has a rim and water flowsdirectly from the first tank adjacent the rim to the clarifying thirdtank.
 40. A method of dewatering a mineral slurry comprising mineralfines, contaminants and comprising the steps of: (a) providing a tankhaving a base surface and introducing said mixture of mineral fines,water, and contaminants to said tank and allowing said mineral fines tosettle on said base surface; (b) removing the mineral fines from saidbase surface of said tank along with water and contaminants and thenseparating said water and at least some of said contaminants from saidmineral fines wherein said separated contaminants are suspended in saidseparated water; (c) adding an agent selected from one or more of thegroup consisting of a coagulant and a flocculent to said water andsuspended contaminants separated from the coal tailings in step (b); (d)allowing the agent added in step (c) to coagulate or flocculate with thesuspended contaminants to form a coagulated or flocculated mass and aquantity of supernatant water; and (e) separating the coagulated orflocculated mass formed in step (d) from the quantity of supernatantwater formed in step (d).
 41. The method of claim 40 wherein the tankhas an entry point where the mixture of mineral fines, water andcontaminants are introduced to the tank in step (a) and a dischargepoint where the mineral fines, water and contaminants are removed instep (b) and said entry point and discharge point are both elevated fromthe base surface and said entry point is laterally displaced from saiddischarge point.
 42. The method of claim 41 wherein the mixture ofmineral fines, water and contaminants is continuously introduced to thetank in step (a) and the mineral fines, water and contaminants arecontinuously removed from the tank in step (b).
 43. The method of claim42 wherein the mineral fines, water and contaminants are continuouslyremoved from the tank by means of a continuous conveyor system.
 44. Themethod of claim 40 wherein in step (b) the mineral fines are separatedfrom the water and contaminants by means of a centrifuge.
 45. The methodof claim 44 wherein at least some of the contaminants removed with thecoal tailings and water in step (b) are suspended in said removed water.46. The method of claim 44 wherein at least some of the contaminantsremoved with the mineral fines and water in step (b) are initiallyadhered to the mineral fines and are then removed from said mineralfines by centrifution to be suspended in the said removed water.
 47. Themethod of claim 40 wherein in step (c) one or more of the groupconsisting of a coagulant and a flocculent is a flocculent and theflocculent is selected from the group consisting of a cationic polymer,an anionic polymer, and a nonionic emulsion polymer.
 48. The method ofclaim 47 wherein in step (c) the flocculent is used in an amount of fromabout 2 percent to about 6 percent by weight of the water and thesuspended contaminants.
 49. The method of claim 40 wherein thecontaminants include clay.
 50. The method of claim 40 wherein in step(c) the water and the suspended solid contaminants are introduced to aclarifying second tank wherein coagulation or flocculation in saidsecond tank in step (d) takes place.
 51. The method of claim 40 whereinthe coagulated or flocculated mass formed in claim (d) contains anadditional quantity of water and at least some of said additionalquantity of water is removed from the coagulated or flocculated massafter said coagulated or flocculated mass is separated from the quantityof supernatant water in step (e).
 52. The method of claim 51 wherein atleast some of said additional quantity of water is removed from thecoagulated or flocculated mass in a press.
 53. The method of claim 51wherein the quantity of supernatant water and the additional quantity ofwater separated from the coagulated or flocculated mas which aresubstantially free of contaminants.
 54. The method of claim 40 whereinin step (a), before being introduced to the first tank, the water in themixture is adjusted so that the mixture is from about 60 percent toabout 90 percent by weight water.
 55. The method of claim 40 wherein thecoal tailings, contaminants and water removed from the tank in step (b)is from about 10 percent to about 40 percent by weight water.
 56. Themethod of claim 50 wherein in step (c) the water and suspendedcontaminants separated from the coal tailing in step (b) is firstremoved to a settling third tank after which the agent selected from oneor more of the group consisting of a coagulant and a flocculent is addedbefore said water and suspended contaminants are added to the clarifyingsecond tank.
 57. The method of claim 50 wherein the first tank has a rimand water flows directly from the first tank adjacent the rim to theclarifying third tank.
 58. A method of recovering water from a mixtureof particulate material, water and solid contaminants consisting of thegroup consisting of coal tailing and water mixtures, substantially cleancoal slurries and mineral slurries comprising the steps of: (a)providing a first tank having a base surface and introducing saidmixture of particulate material, water, and contaminants to said tankand allowing said particulate material to settle on said base surface;(b) removing the particulate material from said base surface of saidtank along with water and contaminants and then separating said waterand at least some of said contaminants from said particulate materialwherein said separated contaminants are suspended in said separatedwater; (c) providing a second tank and a means for removing overflowwater from said first tank to said second tank and allowing water toflow directly from said first tank to said second tank; (d) adding anagent selected from one or more of the group consisting of a coagulantand a flocculent to said water and suspended contaminants separated fromthe particulate material in step (b) and adding said water and suspendedcontaminants to said second tank; (e) allowing the agent added in step(d) to coagulate or flocculate with the suspended contaminants to form acoagulated or flocculated mass and a quantity of supernatant water; and(f) separating the coagulated or flocculated mass formed in step (e)from the quantity of supernatant water formed in step (e).
 59. Themethod of claim 58 wherein the tank has an entry point where the mixtureof tailings, water and contaminants are introduced to the tank in step(a) and a discharge point where the particulate material, water andcontaminants are removed in step (b) and said entry point and dischargepoint are both elevated from the base surface and said entry point islaterally displaced from said discharge point.
 60. The method of claim59 wherein the mixture of particulate material, water and contaminantsis continuously introduced to the tank in step (a) and the particulatematerial, water and contaminants are continuously removed from the tankin step (b).
 61. The method of claim 60 wherein the particulatematerial, water and contaminants are continuously removed from the tankby means of a continuous conveyor system.
 62. The method of claim 58wherein in step (b) the particulate material is separated from the waterand contaminants by means of a centrifuge.
 63. The method of claim 58wherein in step (d) one or more of the group consisting of a coagulantand a flocculent is a flocculent and the flocculent is selected from thegroup consisting of a cationic polymer and an anionic polymer.
 64. Themethod of claim 63 wherein in step (d) the flocculent is used in anamount of from about 2 percent to about 6 percent by weight of the waterand the suspended contaminants.
 65. The method of claim 58 wherein thecontaminants include clay.
 66. The method of claim 58 wherein thecoagulated or flocculated mass formed in claim (e) contains anadditional quantity of water and at least some of said additionalquantity of water is removed from the coagulated or flocculated massafter said coagulated or flocculated mass is separated from the quantityof supernatant water in step (f).
 67. The method of claim 66 wherein atleast some of said additional quantity of water is removed from thecoagulated or flocculated mass in a press.
 68. The method of claim 66wherein the quantity of supernatant water and the additional quantity ofwater separated from the coagulated or flocculated mas which aresubstantially free of contaminants.
 69. An apparatus for use inprocessing a liquid and at least one solid particulate material mixedwith in said liquid said apparatus comprising: a tank having a front endand a rear end, a base surface and a peripheral wall; an input pointpositioned adjacent the rear end of the tank extending generallyupwardly from and surrounding the base wall; an output point positionedadjacent the front end of the; a particle collection area positioned onthe base surface beneath the input point; and means for conveying theparticles extending from adjacent the particle collection area to theoutput point.
 70. The apparatus of claim 69 wherein the means forconveying the particles is a continuous conveyor means having aplurality of particle engagement means.
 71. The apparatus of claim 70wherein the continuous conveyor means is a conveyor chain and theparticle engagement means are paddles perpendicularly extending from theconveyor chain.
 72. The apparatus of claim 71 wherein the continuousconveyor means extends upwardly and forwardly from the particlecollection area to the output point and then rearwardly to adjacent therear end of the tank and then downwardly back to the particle connectionarea.
 73. The apparatus of claim 72 wherein there is a ramp inclinedupwardly and forwardly from adjacent the particle collection area to thefront end of the tank and the continuous conveyor means extends upwardlyand forwardly in spaced relation above said ramp.
 74. The apparatus ofclaim 73 wherein the continuous conveyor is parallel to the ramp. 75.The apparatus of claim 69 wherein the tank has an upper rim and theinput point is positioned adjacent said upper rim of the tank.
 76. Theapparatus of claim 69 wherein the peripheral wall has an upper rim andthe input point is positioned adjacent the upper rim.
 77. The apparatusof claim 77 wherein the means for conveying the particles extends fromthe output point to a particle and liquid separator means.
 78. Theapparatus of claim 77 wherein the particle and liquid separator means isa centrifuge.
 79. The apparatus of claim 78 wherein there is a means foradding an agent selected from one or more of the group of a coagulantand a flocculent and a liquid conveying line extends from the particleand liquid separator means to said means for adding an agent selectedfrom one or more of a coagulent and a flocculent.
 80. The apparatus ofclaim 79 wherein the means for adding an agent selected from one or moreof the group consisting of a coagulant and a flocculent is a polymeraddition means.
 81. The apparatus of claim 79 wherein a liquid conveyingline extends from the means for adding an agent selected from one ormore of the group consisting of a coagulant and a flocculent to aclarifier tank.
 82. The apparatus of claim 81 wherein there is a liquidconveying line provided to remove supernatant water from the clarifiertank.
 83. The apparatus of claim 82 wherein there is a means forremoving a coagulated or flocculated mass containing water from theclarifier tank and for separating said water from said coagulated orflocculated mass.
 84. The apparatus of claim 83 wherein the means forseparating said water from said coagulated or flocculated mass is afilter press.
 85. The apparatus of claim 79 wherein a fluid conveyingmeans connects the first tank and the clarifier tank and said fluidconveying line is remote from the particle collection area in the firsttank.
 86. The apparatus of claim 85 wherein the first tank has an upperrim and the fluid conveying means is a trough extending from theadjacent rim to the clarifier tank.
 87. The apparatus of claim 69wherein the apparatus is truck mounted.
 88. The apparatus of claim 81wherein the clarifier tank is truck mounted.
 89. An apparatus for use inprocessing a liquid and at least one solid particulate material mixedwith said liquid comprising: a first tank having a front end and a rearend, a base surface and a peripheral wall; an input point positionedadjacent the rear end of the first tank extending generally upwardlyfrom and surrounding the base wall; a particle collection areapositioned on the base surface beneath the input point; means forseparating particles and water; means for conveying particles and waterextending from adjacent the particle collection area to the means forseparating particles from water; a second tank connected by a liquidconveyance means directly to the first tank; means for conveying waterfrom the means for separating particles and water to the second tank;means to adding an agent selected from a coagulant and a flocculent tothe water in the second tank; means for recovering water from the secondtank; and means for recovering a coagulated or a flocculated mass fromthe second tank.
 90. An apparatus for reducing the concentration ofparticulate material in a liquid, wherein said particulate material issuspended in said liquid, said apparatus comprising: a flow cavityhaving an input opening and a perforated wall having an outer surface;means for delivering the liquid with suspended particles to the inputopening of the flow cavity under sufficient pressure to cause saidliquid with suspended solids to flow from the input opening to theoutput opening; and whereby the liquid with a decreased concentration ofparticulate material is recovered on the outer surface of the perforatedwall.
 91. The apparatus of claim 90 wherein the flow cavity has anoutput opening and particulate material is recovered at said outputopening.
 92. The apparatus of claim 90 wherein the flow cavity isinclined upwardly from the input opening to the output cavity.
 93. Theapparatus of claim 90 wherein the perforated wall has an adjacenttextile layer.
 94. The apparatus of claim 93 wherein the perforated wallis comprised of an outer plate with a plurality of perforations and alower plate with a plurality of perforations aligned with theperforating in the upper plate and a textile layer interposed betweensaid upper and lower plates.
 95. The apparatus of claim 90 wherein aplunger is provided in the flow cavity to move particles and liquid fromthe input opening to the output opening.
 96. An apparatus for reducingthe concentration of particulate material in a liquid, wherein saidparticulate material is suspended in said liquid, said apparatuscomprising: a flow cavity having an input opening and a restrictedoutput opening and a perforated wall having an outer surface; means fordelivering the liquid with suspended particles to the input opening ofthe flow cavity under sufficient pressure to cause said liquid withsuspended solids to flow from the input opening to the output opening ofsaid flow cavity; means for adjustably elevating the output opening ofthe flow cavity above the input opening of the flow cavity; A trough forrecovering liquid with a reduced concentration of particulate materialfrom the outer surface of the perforated wall of the flow cavity; and asurface for recovering particulate material from the output opening ofthe flow cavity.
 97. The apparatus of claim 96 wherein a plunger isprovided in the flow cavity to move particles and liquid from the inputopening to the output opening.
 98. An apparatus for use in processing aliquid and solid particles mixed with said liquid comprising: a firsttank having a front end and a rear end, a base surface and a peripheralwall; an input point positioned adjacent the rear end of the first tankextending generally upwardly from and surrounding the base wall; aparticle collection area positioned on the base surface beneath theinput point; means for separating some of the particles from the waterto produce water with suspended particles and separated particles; meansfor conveying particles and water extending from adjacent the particlecollection area to the means for separating particles from water; asecond tank connected by a liquid conveyance means directly to the firsttank; means for conveying water with suspended particles from the meansfor separating some of the particles and water to the second tank; meansfor adding an agent selected from a coagulant and a flocculent to thewater in the second tank; means for reducing the concentration of theparticles in the liquid with suspended particles comprising: a flowcavity having an input opening, an output opening and a perforated wallhaving an outer surface; means for delivering the liquid with suspendedparticles to the input opening of the flow cavity under sufficientpressure to cause said liquid with suspended solids to flow from theinput opening to the output opening; whereby the liquid with a decreasedconcentration of particles is recovered on the outer surface of theperforated wall of the flow cavity and particles are recovered at theoutput opening of the flow cavity; and means for conveying liquid withsuspended particles from the second tank to the means for reducing theconcentration of the particles in the liquid with suspended particles.